1. Field of the Invention
This invention relates to a tilt switch, more particularly to a tilt switch which is adapted to be mounted on a support and which has an electrically conductive ball rollable to make or break an electrical connection between two electric contact terminals.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional tilt switch 10 is shown to include a rectangular insulating housing 11 with an accommodation chamber therein for receiving rollably an electrically conductive ball 12. Two pairs of first and second electric contact terminals 13 are press-fitted to a bottom plug 14, and have upper tip ends 131 extending into the accommodation chamber of the housing 11 when the bottom plug 14 is secured to a bottom opening 111 of the housing 11 by virtue of engagement between protrusions 112 and recesses 142. A seal member 114 is disposed to seal a clearance 113 between the housing 11 and the bottom plug 14. Lower tip ends 132 of the terminals 13 are soldered on an electric contact member of a support (not shown). When the tilt switch 10 is mounted on the support, which stands on a horizontal plane 20, the ball 12 contacts the upper tip ends 131 to make an electrical connection between the first and second electric contact terminals 13. Once the support is tilted, the ball 12 will roll away from the terminals 13 to break the electrical connection.
The housing 11 has an inner peripheral wall surface 115 extending uprightly to confine the elongated accommodating chamber such that the ball 12 is rollable thereon. It is noted that the movement of the ball 12 is somewhat difficult away from the terminals 13 in the state that the housing 11 is not tilted down completely, thereby resulting in lack of safety during use.
The object of the present invention is to provide a tilt switch which can provide adequate protection to an electrical appliance.
According to this invention, the tilt switch includes an insulating housing adapted to be mounted on a support in an upright direction. The housing has an inner bottom wall surface, and an inner peripheral wall surface which extends upwardly from a periphery of the inner bottom wall surface and which confines an accommodating chamber therein. The inner peripheral wall surface includes a lower segment which is proximate to the periphery of the inner bottom wall surface and which defines a first diameter, an upper segment which is disposed opposite to the lower segment in the upright direction and which defines a second diameter larger than the first diameter, and an annular shoulder segment which extends between and which interconnects the upper and lower segments so as to define an annular juncture between the lower and shoulder segments. First and second electric contact terminals are secured in the housing at middle portions thereof. Each of the first and second electric contact terminals has an upper end portion which extends upwardly from the middle portion into the accommodation chamber through the inner bottom wall surface to form a contact surface spaced apart from the bottom wall surface, and a lower end portion which extends downwardly from the middle portion and outwardly of the housing to be adapted to establish electrical connection with the support. The contact surfaces of the first and second electric contact terminals are spaced apart from each other in a transverse direction relative to the upright direction. An electrically conductive ball is received rollably in the accommodation chamber, and is of such a dimension as to contact the contact surfaces when the housing stands in an upright position, thereby making an electrical connection between the first and second electric contact terminals. The ball defines a first horizontal plane at which a center of the ball is located. The annular juncture is located at a second horizontal plane lower than the first horizontal plane such that once the housing is tilted from an upright position, the ball will move over the annular juncture to the shoulder segment so as to break the electrical connection between the first and second electric contact terminals.